Carcinogenesis is thought to be induced by mutation on oncogenes and tumor suppresser genes. However major mutagens/carcinogens present in our environment and formed endogenously are still unclear. The purpose of our study is to clarify novel mutagens/carcinogens and antimutagens which attenuate/invalidate those genotoxic compounds. The ultimate goal of our study is to contribute to prevent carcinogenesis. In addition, we are investigating the relationships between symptoms of asthma and air pollution. To clarify the asthma-causing air pollutant, we started collaborative research with researchers working in other research institutes and hospitals.